class Handwriting {
	// 内置数据
	ctx = '';
	canvasWidth = 300;
	canvasHeight = 900;
	linePrack = []; //划线轨迹 ; 生成线条的实际点
	currentLine = [];
	transparent = 1; // 透明度
	pressure = 0.5; // 默认压力
	smoothness = 100; //顺滑度，用60的距离来计算速度
	lineSize = 1.5; // 笔记倍数
	lineMin = 0.5; // 最小笔画半径
	lineMax = 2; // 最大笔画半径
	currentPoint = {};
	firstTouch = true; // 第一次触发
	radius = 1; //画圆的半径
	cutArea = {
		top: 0,
		right: 0,
		bottom: 0,
		left: 0
	}; //裁剪区域
	lastPoint = 0;
	chirography = []; //笔迹
	startY = 0;
	deltaY = 0;
	startValue = 0;
	constructor(opts) {
		// console.log(opts);
		this.penColor = opts.penColor || '#1A1A1A' // 颜色
		this.slideValue = opts.slideValue || 50
		this.canvasName = opts.canvasName || 'handWriting'
		this.ctx = opts.ctx
		this.init()
	}
	init() {
		this.selectSlideValue(this.slideValue);
	}

	setSize(rect) {
		this.canvasWidth = rect.width
		this.canvasHeight = rect.height
	}

	// 笔迹开始
	uploadScaleStart(event) {
		// console.log('start', event);
		let e = event.mp || event;
		if (e.type != 'touchstart') return false;

		this.ctx.setFillStyle(this.penColor); // 初始线条设置颜色
		this.ctx.setGlobalAlpha(this.transparent); // 设置半透明
		this.currentPoint = {
			x: e.touches[0].x,
			y: e.touches[0].y
		}
		this.currentLine.unshift({
			time: new Date().getTime(),
			dis: 0,
			x: this.currentPoint.x,
			y: this.currentPoint.y
		})
		if (this.firstTouch) {
			this.cutArea = {
				top: this.currentPoint.y,
				right: this.currentPoint.x,
				bottom: this.currentPoint.y,
				left: this.currentPoint.x
			}
			this.firstTouch = false
		}
		this.pointToLine(this.currentLine);
	}
	// 笔迹移动
	uploadScaleMove(event) {
		// console.log('move', event);
		let e = event.mp || event;
		if (e.type != 'touchmove') return false;
		if (e.cancelable) {
			// 判断默认行为是否已经被禁用
			if (!e.defaultPrevented) {
				e.preventDefault();
			}
		}
		let point = {
			x: e.touches[0].x,
			y: e.touches[0].y
		}
		//测试裁剪
		if (point.y < this.cutArea.top) {
			this.cutArea.top = point.y;
		}
		if (point.y < 0) this.cutArea.top = 0;

		if (point.x > this.cutArea.right) {
			this.cutArea.right = point.x;
		}
		if (this.canvasWidth - point.x <= 0) {
			this.cutArea.right = this.canvasWidth;
		}
		if (point.y > this.cutArea.bottom) {
			this.cutArea.bottom = point.y;
		}
		if (this.canvasHeight - point.y <= 0) {
			this.cutArea.bottom = this.canvasHeight;
		}
		if (point.x < this.cutArea.left) {
			this.cutArea.left = point.x;
		}
		if (point.x < 0) this.cutArea.left = 0;

		this.lastPoint = this.currentPoint;
		this.currentPoint = point
		this.currentLine.unshift({
			time: new Date().getTime(),
			dis: this.distance(this.currentPoint, this.lastPoint, 'move'),
			x: point.x,
			y: point.y
		})
		this.pointToLine(this.currentLine);
	}
	// 笔迹结束
	uploadScaleEnd(event) {
		// console.log('end', event);
		let e = event.mp || event;
		if (e.type != 'touchend') return 0;
		// console.log(e);
		let point = {
			x: e.changedTouches[0].x,
			y: e.changedTouches[0].y
		}

		this.lastPoint = this.currentPoint;
		this.currentPoint = point
		this.currentLine.unshift({
			time: new Date().getTime(),
			dis: this.distance(this.currentPoint, this.lastPoint, 'end'),
			x: point.x,
			y: point.y
		})
		if (this.currentLine.length > 2) {
			var info = (this.currentLine[0].time - this.currentLine[this.currentLine.length - 1].time) / this.currentLine.length;
			//$("#info").text(info.toFixed(2));
		}
		//一笔结束，保存笔迹的坐标点，清空，当前笔迹
		//增加判断是否在手写区域；
		this.pointToLine(this.currentLine);
		var currentChirography = {
			lineSize: this.lineSize,
			penColor: this.penColor
		};
		this.chirography.unshift(currentChirography);
		this.linePrack.unshift(this.currentLine);
		this.currentLine = []
	}
	retDraw() {
		this.ctx.clearRect(0, 0, this.canvasWidth || 700, this.canvasHeight || 730)
		this.ctx.draw()
		this.cutArea = {
			top: 0,
			right: 0,
			bottom: 0,
			left: 0
		}; 
		this.firstTouch = true
	}

	clear() {
		this.linePrack = []
		this.currentLine = []
		this.retDraw()
	}

	isEmpty() {
		return this.linePrack.length === 0
	}

	//画两点之间的线条；参数为:line，会绘制最近的开始的两个点；
	pointToLine(line) {
		this.calcBethelLine(line);
		return;
	}
	//计算插值的方式；
	calcBethelLine(line) {
		if (line.length <= 1) {
			line[0].r = this.radius;
			return;
		}
		let x0, x1, x2, y0, y1, y2, r0, r1, r2, len, lastRadius, dis = 0,
			time = 0,
			curveValue = 0.5;
		if (line.length <= 2) {
			x0 = line[1].x
			y0 = line[1].y
			x2 = line[1].x + (line[0].x - line[1].x) * curveValue;
			y2 = line[1].y + (line[0].y - line[1].y) * curveValue;
			//x2 = line[1].x;
			//y2 = line[1].y;
			x1 = x0 + (x2 - x0) * curveValue;
			y1 = y0 + (y2 - y0) * curveValue;;

		} else {
			x0 = line[2].x + (line[1].x - line[2].x) * curveValue;
			y0 = line[2].y + (line[1].y - line[2].y) * curveValue;
			x1 = line[1].x;
			y1 = line[1].y;
			x2 = x1 + (line[0].x - x1) * curveValue;
			y2 = y1 + (line[0].y - y1) * curveValue;
		}
		//从计算公式看，三个点分别是(x0,y0),(x1,y1),(x2,y2) ；(x1,y1)这个是控制点，控制点不会落在曲线上；实际上，这个点还会手写获取的实际点，却落在曲线上
		len = this.distance({
			x: x2,
			y: y2
		}, {
			x: x0,
			y: y0
		}, 'calc');
		lastRadius = this.radius;
		for (let n = 0; n < line.length - 1; n++) {
			dis += line[n].dis;
			time += line[n].time - line[n + 1].time;
			if (dis > this.smoothness) break;
		}
		this.radius = Math.min(time / len * this.pressure + this.lineMin, this.lineMax) * this.lineSize
		line[0].r = this.radius;
		//计算笔迹半径；
		if (line.length <= 2) {
			r0 = (lastRadius + this.radius) / 2;
			r1 = r0;
			r2 = r1;
			//return;
		} else {
			r0 = (line[2].r + line[1].r) / 2;
			r1 = line[1].r;
			r2 = (line[1].r + line[0].r) / 2;
		}
		let n = 5;
		let point = [];
		for (let i = 0; i < n; i++) {
			let t = i / (n - 1);
			let x = (1 - t) * (1 - t) * x0 + 2 * t * (1 - t) * x1 + t * t * x2;
			let y = (1 - t) * (1 - t) * y0 + 2 * t * (1 - t) * y1 + t * t * y2;
			let r = lastRadius + (this.radius - lastRadius) / n * i;
			point.push({
				x: x,
				y: y,
				r: r
			});
			if (point.length == 3) {
				let a = this.ctaCalc(point[0].x, point[0].y, point[0].r, point[1].x, point[1].y, point[1].r, point[2].x, point[2].y,
					point[2].r);
				a[0].color = this.penColor;
				this.bethelDraw(a, 1);
				point = [{
					x: x,
					y: y,
					r: r
				}];
			}
		}
	}
	//求两点之间距离
	distance(a, b, type) {
		let x = b.x - a.x;
		let y = b.y - a.y;
		return Math.sqrt(x * x + y * y) * 5;
	}
	ctaCalc(x0, y0, r0, x1, y1, r1, x2, y2, r2) {
		let a = [],
			vx01, vy01, norm, n_x0, n_y0, vx21, vy21, n_x2, n_y2;
		vx01 = x1 - x0;
		vy01 = y1 - y0;
		norm = Math.sqrt(vx01 * vx01 + vy01 * vy01 + 0.0001) * 2;
		vx01 = vx01 / norm * r0;
		vy01 = vy01 / norm * r0;
		n_x0 = vy01;
		n_y0 = -vx01;
		vx21 = x1 - x2;
		vy21 = y1 - y2;
		norm = Math.sqrt(vx21 * vx21 + vy21 * vy21 + 0.0001) * 2;
		vx21 = vx21 / norm * r2;
		vy21 = vy21 / norm * r2;
		n_x2 = -vy21;
		n_y2 = vx21;
		a.push({
			mx: x0 + n_x0,
			my: y0 + n_y0,
			color: "#1A1A1A"
		});
		a.push({
			c1x: x1 + n_x0,
			c1y: y1 + n_y0,
			c2x: x1 + n_x2,
			c2y: y1 + n_y2,
			ex: x2 + n_x2,
			ey: y2 + n_y2
		});
		a.push({
			c1x: x2 + n_x2 - vx21,
			c1y: y2 + n_y2 - vy21,
			c2x: x2 - n_x2 - vx21,
			c2y: y2 - n_y2 - vy21,
			ex: x2 - n_x2,
			ey: y2 - n_y2
		});
		a.push({
			c1x: x1 - n_x2,
			c1y: y1 - n_y2,
			c2x: x1 - n_x0,
			c2y: y1 - n_y0,
			ex: x0 - n_x0,
			ey: y0 - n_y0
		});
		a.push({
			c1x: x0 - n_x0 - vx01,
			c1y: y0 - n_y0 - vy01,
			c2x: x0 + n_x0 - vx01,
			c2y: y0 + n_y0 - vy01,
			ex: x0 + n_x0,
			ey: y0 + n_y0
		});
		a[0].mx = a[0].mx.toFixed(1);
		a[0].mx = parseFloat(a[0].mx);
		a[0].my = a[0].my.toFixed(1);
		a[0].my = parseFloat(a[0].my);
		for (let i = 1; i < a.length; i++) {
			a[i].c1x = a[i].c1x.toFixed(1);
			a[i].c1x = parseFloat(a[i].c1x);
			a[i].c1y = a[i].c1y.toFixed(1);
			a[i].c1y = parseFloat(a[i].c1y);
			a[i].c2x = a[i].c2x.toFixed(1);
			a[i].c2x = parseFloat(a[i].c2x);
			a[i].c2y = a[i].c2y.toFixed(1);
			a[i].c2y = parseFloat(a[i].c2y);
			a[i].ex = a[i].ex.toFixed(1);
			a[i].ex = parseFloat(a[i].ex);
			a[i].ey = a[i].ey.toFixed(1);
			a[i].ey = parseFloat(a[i].ey);
		}
		return a;
	}
	bethelDraw(point, is_fill, color) {
		this.ctx.beginPath();
		this.ctx.moveTo(point[0].mx, point[0].my);
		if (undefined != color) {
			this.ctx.setFillStyle(color);
			this.ctx.setStrokeStyle(color);
		} else {
			this.ctx.setFillStyle(point[0].color);
			this.ctx.setStrokeStyle(point[0].color);
		}
		for (let i = 1; i < point.length; i++) {
			this.ctx.bezierCurveTo(point[i].c1x, point[i].c1y, point[i].c2x, point[i].c2y, point[i].ex, point[i].ey);
		}
		this.ctx.stroke();
		if (undefined != is_fill) {
			this.ctx.fill(); //填充图形 ( 后绘制的图形会覆盖前面的图形, 绘制时注意先后顺序 )
		}
		this.ctx.draw(true)
	}

	selectColorEvent(penColor) {
		this.penColor = penColor;
	}

	selectSlideValue(slideValue) {
		switch (slideValue) {
			case 0:
				this.lineSize = 0.1;
				this.lineMin = 0.1;
				this.lineMax = 0.1;
				break;
			case 25:
				this.lineSize = 1;
				this.lineMin = 0.5;
				this.lineMax = 2;
				break;
			case 50:
				this.lineSize = 1.5;
				this.lineMin = 1;
				this.lineMax = 3;
				break;
			case 75:
				this.lineSize = 1.5;
				this.lineMin = 2;
				this.lineMax = 3.5;
				break;
			case 100:
				this.lineSize = 3;
				this.lineMin = 2;
				this.lineMax = 3.5;
				break;
		}
	}
	// TODO 回显签名
	fromDataURL(dataUrl, options = {}) {
		// console.log('APP ===>')
		// uni.chooseImage({
		//   success: (res) => {
		//     this.ctx.drawImage(res.tempFilePaths[0], 0, 0, 150, 100)
		//     this.ctx.draw()
		//   }
		// })
		
		// return new Promise((resolve, reject) => {
			const width = options.width || this.canvas.width;
			const height = options.height || this.canvas.height;
			const xOffset = options.xOffset || 0;
			const yOffset = options.yOffset || 0;
			// 记录当前图片的区位
			this.cutArea = {
				left: xOffset + 2.5,
				top: yOffset + 2,
				right: xOffset + width + 2,
				bottom: yOffset + height + 2
			}
			this.firstTouch = false;
			
			this.ctx.drawImage(dataUrl, xOffset, yOffset);
			this.ctx.draw();
			
			// 纯粹为了判断是否为空时表示不为空 @isEmpty()
			this.linePrack.push({});			
		// });
	}
}

export default Handwriting;